Re: Arbitrary vector

*To*: mathgroup at smc.vnet.net*Subject*: [mg121695] Re: Arbitrary vector*From*: Simon <simonjtyler at gmail.com>*Date*: Mon, 26 Sep 2011 04:15:00 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*References*: <j5hd9m$7fq$1@smc.vnet.net>*Reply-to*: comp.soft-sys.math.mathematica at googlegroups.com

It's not built into Mathematica. But it is possible to define the rules that you need for your calculation - either in terms of symbolic matrices or some symbolic index notation. I don't know of any good implementation of symbolic matrices - but here's an ugly one of mine: http://stackoverflow.com/q/5708208/421225 It needs a lot of work (I've got a half-rewritten copy of it on my machine using optional values instead of options that makes it a little tidier), but you get the idea. As for index notation, there is xAct (http://xact.es/) which is mainly focused on general relativity - but you can define a flat R^n space... There are definitely other implementations of symbolic (indexed and non-indexed) matrices, but I can't remember where or how good they are. Simon